1. Field of the Invention
The present invention relates to a drill, in particular, for a hammer drill for drilling in stone, concrete and the like and including a stem and a drilling head formed of a hard material and provided, at its first end with at lest one main bit having a tip, and at a second end located opposite the first end with a bottom surface for mounting the drilling head on the stem, and having a plurality of axially extending through-grooves for removing drillings produced during a drilling process.
2. Background of the Invention
In order to provide for transition of drillings, which are produced by bits during a drilling process, toward the drill helices without a flow resistance, the drilling heads are provided with through-grooves. With a drill diameter in a range from 5 mm to 17 mm, the through-grooves have, in particular in one-piece drilling heads formed of a hard material, e.g., a hard metal, a constant cross-section over the entire axial extent of the drilling head.
A drawback of the drilling heads consists in that upon formation and removal of drillings, the density is changed, which can lead to an impediment to removal of the drillings. Furthermore, with drills having a diameter in the range from 5 to 17 mm in particular, a secondary comminution beneath the bits takes place, with results in very fine drilling dust if the produced drillings are not transferred in the drill helix sufficiently rapidly. The drilling dust causes a large contamination around and outside of bore edges which is highly undesirable, in particular during works in residential areas or offices.
U.S. Pat. No. 5,893,688 discloses a drill having a drilling head with a hard metal insert and with helical grooves extending up to the free end surface of the drilling head. In this drill, an efficient removal of drillings, which are produced during a drilling process, takes place. In one-piece drilling heads formed of a hard material and having, in particular, a diameter in a range from 5 mm to 17 mm, for manufacturing reasons, helical grooves of the drill stem cannot extend up to the free end surface of the drilling head.
British patent Publication GB 2075 409A discloses a drill having a drilling head with a hard metal insert and through-grooves are tilted relative to the axial extent of the drill. In this drill, the removal of the produced drillings is improved in comparison with removal of drillings in a drill having a drilling head with axially extending through-grooves. However, in this drills, a secondary comminution still takes place which, as it has been discussed above, is highly undesirable.
Accordingly, an object of the present invention is to provide a drill having a one-piece drilling head formed of a hard material and in which the above-discussed drawbacks of the known drill are eliminated.
Another object of the present invention is to provide a drill with a one-piece drilling head formed of a hard material and in which an efficient removal of drillings is possible, with simultaneous reduction of secondary comminution.